什么意思是“不在某些外壳下运行”？在Perl脚本中？ [英] What means "not running under some shell" in Perl scripts?

问题描述

在许多perl脚本中（尤其是在著名的CPAN发行版中），我发现以下代码：

In many perl scripts (especially in famous CPAN distros) I find the following piece of code:

eval 'exec /usr/bin/perl -w -S $0 ${1+"$@"}'
if 0; # not running under some shell

我想知道它的用途是什么？

I was wondering what it is for?

谢谢。

推荐答案

某些系统无法识别＃！ / usr / bin / perl 脚本开头的行，因此，在这样的系统上尝试通过名称调用Perl程序会将脚本传递给shell。为了解决这个问题，可移植的Perl程序以一行开头，当由标准POSIX shell解释时，该行将脚本传递给 perl（1）。 if 0 导致当由Perl本身运行时该行被忽略，而将其放在单独的行上会使Shell将其视为单独的命令，仅运行 eval'exec / usr / bin / perl -w -S $ 0 $ {1 + $ @}''一旦被读取。

Some systems don't recognize the #!/usr/bin/perl line at the start of scripts, and so trying to invoke a Perl program by name on such a system will simply pass the script to the shell. In order to combat this, portable Perl programs begin with a line that, when interpreted by a standard POSIX shell, causes the script to be passed to perl(1) instead. The if 0 causes the line to be ignored when run by Perl itself, and placing it on a separate line causes shells to treat it as a separate command, running just the eval 'exec /usr/bin/perl -w -S $0 ${1+"$@"}' as soon as it's read.

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